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  • 1
    Digitale Medien
    Digitale Medien
    Initiation of long, free-standing z discharges by CO2 laser gas heating (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 617-623 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beam fusion reactor. At the Gesellschaft fuer Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia (NH3) gas are initiated by a CO2 laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the v2 vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high current discharge was investigated. This article describes the laser–gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1426239
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  • 2
    Digitale Medien
    Digitale Medien
    Nanopatterning of copper (111) vicinal surfaces by oxygen-induced mesoscopic faceting (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2686-2688 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the preparation of periodic nanostripes on vicinal copper surfaces. For the investigated Cu(n,n,n−1) surfaces [n=4,3,2], an oxygen-induced mesoscopic faceting of the regular monoatomic stepped surfaces into periodic nanostripes consisting of Cu(111) and Cu(110)–O(2×1) facets is observed. The width and thermal stability of these nanostripes increase with the terrace length of the initial vicinal surfaces. Stripe widths of 50, 20, and 12 nm were obtained for Cu(443), Cu(332), and Cu(221), respectively. Whereas on Cu(221) the nanostripes disappear above 450 K, they are stable up to 800 K on Cu(443). For the latter surface, the nanostructures are found to be unusually stable and could be observed ex situ by atomic force microscopy under ambient conditions. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.126444
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  • 3
    Digitale Medien
    Digitale Medien
    STUDIES ON ENZYMATIC TENDERIZATION OF MEAT. III. HISTOLOGICAL AND PANEL ANALYSES OF ENZYME PREPARATIONS FROM THREE DISTINCT SOURCES (1958)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 23 (1958), S. 0 
    Details
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2621.1958.tb17590.x
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  • 4
    Digitale Medien
    Digitale Medien
    Evaluation of immunotherapy-induced changes in specific IgE, IgG and IgG subclasses in birch pollen allergic patients by means of immunoblotting (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 45 (1990), S. 0 
    Details
    ISSN: 1398-9995
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Sera from 27 birch pollen-allergic patients who had undergone hyposensitization treatment for 22–41 months were studied by immunoblotting before and after therapy, whereby the levels of IgE, IgG and IgG1–4 antibodies directed against the major allergen Bet v I and minor allergens of birch pollen were monitored. The clinical benefit of immunotherapy (IT) was evaluated using a symptom specific questionnaire. In patients with good clinical response (responders, n=18), as defined by improvement of symptoms, anti-Bet v I IgE antibodies were found to decrease in 10/18 patients (55.5%), whereas in 6/18 (33.3%) no change and in two cases (11.2%) an increase of specific IgE was observed. In the group of patients with unsatisfactory clinical outcome (non-responders, n=9), 3/9 patients (33.3%) showed a decrease, 3/9 (33.3%) no change and 3/9 (33.3%) an increase in levels of IgE antibodies directed against Bet v I. In the case of minor allergens, 5/18 responders (27.7%) and 8/9 non-responders (88.8%) showed specific IgE before IT. In the responder group, no increase of specific IgE could be observed after IT. In non-responders, however, an increase of IgE directed against minor allergens was seen in 3/9 patients (33.3%). In all patients, regardless of therapeutical success, IT-induced elevated levels of specific IgG, IgG1 and in particular IgG4 directed against Bet v I vere found. Regarding minor allergens, a heterogeneous pattern of IgG responses without significant correlation to clinical benefit was observed. Our results indicate that changes in IgG reactivity patterns against Bet v I and minor allergens, as shown by the immunoblot technique, did not correlate with good or bad clinical outcome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1398-9995.1990.tb01092.x
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  • 5
    Digitale Medien
    Digitale Medien
    Arcjet plasma plume effect on a microwave reflector antenna : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2978-2980 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A configuration is described to measure the effect of the plasma produced by an arcjet thruster on a reflector antenna. The diagnostic consists of a small movable rf probe coupled to a Hewlett–Packard 8510 network analyzer. Because the perturbation is expected to be small (〈10° phase shift), wall reflections are an important consideration. To minimize their effect we use Fourier transform gating techniques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141745
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  • 6
    Digitale Medien
    Digitale Medien
    Multiple Testing and Data Adaptive Regression: An Application to HIV-1 Sequence Data. (2005)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Statistical applications in genetics and molecular biology 4.2005, 1, art8 
    Details
    ISSN: 1544-6115
    Quelle: Berkeley Electronic Press Academic Journals
    Thema: Biologie
    Notizen: Analysis of viral strand sequence data and viral replication capacity could potentially lead to biological insights regarding the replication ability of HIV-1. Determining specific target codons on the viral strand will facilitate the manufacturing of target-specific antiretrovirals. Various algorithmic and analysis techniques can be applied to this application. In this paper, we apply two techniques to a data set consisting of 317 patients, each with 282 sequenced protease and reverse transcriptase codons. The first application is recently developed multiple testing procedures to find codons which have significant univariate associations with the replication capacity of the virus. A single-step multiple testing procedure (Pollard and van der Laan 2003) method was used to control the family wise error rate (FWER) at the five percent alpha level as well as the application of augmentation multiple testing procedures to control the generalized family wise error (gFWER) or the tail probability of the proportion of false positives (TPPFP). We also applied a data adaptive multiple regression algorithm to obtain a prediction of viral replication capacity based on an entire mutant/non-mutant sequence profile. This is a loss-based, cross-validated Deletion/Substitution/Addition regression algorithm (Sinisi and van der Laan 2004), which builds candidate estimators in the prediction of a univariate outcome by minimizing an empirical risk. These methods are two separate techniques with distinct goals used to analyze this structure of viral data.
    Materialart: Digitale Medien
    URL: http://www.bepress.com/sagmb/vol4/iss1/art8
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  • 7
    Digitale Medien
    Digitale Medien
    Application of a Variable Importance Measure Method (2006)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    The @international journal of biostatistics 2 (2006), S. 6 
    Details
    ISSN: 1557-4679
    Quelle: Berkeley Electronic Press Academic Journals
    Thema: Biologie , Mathematik , Medizin
    Notizen: Van der Laan (2005) proposed a targeted method used to construct variable importance measures coupled with respective statistical inference. This technique involves determining the importance of a variable in predicting an outcome. This method can be applied as inverse probability of treatment weighted (IPTW) or double robust inverse probability of treatment weighted (DR-IPTW) estimators. The variance and respective p-value of the estimate are calculated by estimating the influence curve. This article applies the Van der Laan (2005) variable importance measures and corresponding inference to HIV-1 sequence data. In this application, the method is targeted at every codon position. In this data application, protease and reverse transcriptase codon positions on the HIV-1 strand are assessed to determine their respective variable importance, with respect to an outcome of viral replication capacity. We estimate the DR-IPTW W-adjusted variable importance measure for a specified set of potential effect modifiers W. In addition, simulations were performed on two separate datasets to examine the DR-IPTW estimator.
    Materialart: Digitale Medien
    URL: http://www.bepress.com/ijb/vol2/iss1/6
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  • 8
    Digitale Medien
    Digitale Medien
    Empirical Bayes and Resampling Based Multiple Testing Procedure Controlling Tail Probability of the Proportion of False Positives. (2005)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Statistical applications in genetics and molecular biology 4.2005, 1, art29 
    Details
    ISSN: 1544-6115
    Quelle: Berkeley Electronic Press Academic Journals
    Thema: Biologie
    Notizen: Simultaneously testing a collection of null hypotheses about a data generating distribution based on a sample of independent and identically distributed observations is a fundamental and important statistical problem involving many applications. In this article we propose a new re-sampling based multiple testing procedure asymptotically controlling the probability that the proportion of false positives among the set of rejections exceeds q at level alpha, where q and alpha are user supplied numbers. The procedure involves 1) specifying a conditional distribution for a guessed set of true null hypotheses, given the data, which asymptotically is degenerate at the true set of null hypotheses, and 2) specifying a generally valid null distribution for the vector of test-statistics proposed in Pollard & van der Laan (2003), and generalized in our subsequent article Dudoit, van der Laan, & Pollard (2004), van der Laan, Dudoit, & Pollard (2004), and van der Laan, Dudoit, & Pollard (2004b). Ingredient 1) is established by fitting the empirical Bayes two component mixture model (Efron (2001b)) to the data to obtain an upper bound for marginal posterior probabilities of the null being true, given the data. We establish the finite sample rational behind our proposal, and prove that this new multiple testing procedure asymptotically controls the wished tail probability for the proportion of false positives under general data generating distributions. In addition, we provide simulation studies establishing that this method is generally more powerful in finite samples than our previously proposed augmentation multiple testing procedure (van der Laan, Dudoit, & Pollard (2004b)) and competing procedures from the literature. Finally, we illustrate our methodology with a data analysis.
    Materialart: Digitale Medien
    URL: http://www.bepress.com/sagmb/vol4/iss1/art29
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  • 9
    Digitale Medien
    Digitale Medien
    Issues of Processing and Multiple Testing of SELDI-TOF MS Proteomic Data (2006)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Statistical applications in genetics and molecular biology 5.2006, 1, art11 
    Details
    ISSN: 1544-6115
    Quelle: Berkeley Electronic Press Academic Journals
    Thema: Biologie
    Notizen: A new data filtering method for SELDI-TOF MS proteomic spectra data is described. We examined technical repeats (2 per subject) of intensity versus m/z (mass/charge) of bone marrow cell lysate for two groups of childhood leukemia patients: acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). As others have noted, the type of data processing as well as experimental variability can have a disproportionate impact on the list of ``interesting'' proteins (see Baggerly et al. (2004)). We propose a list of processing and multiple testing techniques to correct for 1) background drift; 2) filtering using smooth regression and cross-validated bandwidth selection; 3) peak finding; and 4) methods to correct for multiple testing (van der Laan et al. (2005)). The result is a list of proteins (indexed by m/z) where average expression is significantly different among disease (or treatment, etc.) groups. The procedures are intended to provide a sensible and statistically driven algorithm, which we argue provides a list of proteins that have a significant difference in expression. Given no sources of unmeasured bias (such as confounding of experimental conditions with disease status), proteins found to be statistically significant using this technique have a low probability of being false positives.
    Materialart: Digitale Medien
    URL: http://www.bepress.com/sagmb/vol5/iss1/art11
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  • 10
    Digitale Medien
    Digitale Medien
    Degradation of polysaccharides by immobilized depolymerizing enzymes (1990)
    Oxford, UK : Blackwell Publishing Ltd
    International journal of food science & technology 25 (1990), S. 0 
    Details
    ISSN: 1365-2621
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Polysaccharides in fruit and vegetable juices can be efficiently degraded using co-immobilized amylolytic and pectolytic enzymes combined with naringinase. The enzymes were immobilized on silica carriers for use in fining procedures to remove cloudiness.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2621.1990.tb01054.x
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